Vaisala WMT700 - Manual (Page 43)

Chapter 3 _______________________________________________________ Functional Description
Figure 14 below shows an example of averaging wind direction
when the measured wind values are 355° and 10°. The resulting
average is 2.5°.
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Figure 14 Example of Wind Direction Averaging
Wind Direction Coasting
Accurate wind direction measurement requires that the wind
speed is sufficient. If you enable wind direction coasting,
WMT700 does not calculate wind direction when the wind speed
drops below the selected wind direction coasting threshold. The
last calculated direction output remains until the wind speed
increases enough to reach the threshold and WMT700 returns to
normal operation.
Vector Averaging
When vector averaging is selected, WMT700 calculates wind
speed and direction averages by adding up each x velocity and y
velocity measurement from the averaging time and then dividing
the sum by the number of measurements. WMT700 converts the
resultant average x velocity and average y velocity to polar
direction and magnitude, which returns the wind direction average
in degrees and wind speed average in the chosen units.
If the data acquisition system requests data before the initial
averaging time completes, the sensor returns the most recent
complete measurement data.
VAISALA ________________________________________________________________________ 41